共查询到18条相似文献，搜索用时 140 毫秒
1.
湖冰厚度是湖泊在封冻期的重要物理参数,明晰其时空变化特征对于认识气候变暖背景下的湖冰响应规律具有重要的理论价值和现实意义.基于ERA5 Climate Reanalysis气温数据集、MODIS MOD09GQ数据产品和2019年湖冰钻孔测厚数据及雷达测厚数据,重建2000—2019年青海湖冰厚时间序列并分析其时空变化特征.结果表明:①2019年3月实测青海湖湖冰厚度平均增长速率为0.30 cm/d,高于2月份(0.12 cm/d).基于度日法湖冰生长模型模拟的2018年11月—2019年3月青海湖冰厚平均增长速率为0.34 cm/d,与实际观测数据相比,模拟冰厚误差为±2 cm,但在河流入湖口处和湖区南侧误差较大,且冰厚模拟数值在3月中旬前高估而之后有所低估.②青海湖多年平均冰厚介于32～37 cm,其中2008—2016年湖冰厚度年际变化剧烈,呈现先增大再稳定后减小的趋势.冻结初期湖冰厚度增长迅速,12月和1月湖冰增长速率分别为0.45和0.41 cm/d,2月后冰厚增长速率放缓,2月和3月分别为0.29和0.14 cm/d.③2000—2019年冰厚整体呈现北厚南薄、东厚西薄的空间格局,多年冰厚变化幅度湖区西部较东部稳定,湖冰平均厚度与完全封冻时长及封冻期呈正相关. 相似文献
2.
应用1999年8月19～24日我国第1次北极考察资料对北极夏季近地层气象要素梯度特征和冰面热量收支问题进行了讨论.北极夏季近地层相对于冰面的相对湿度很大，经常接近于饱和状态，冰温具有明显的日变化，夜间冰面附近冰温梯度较大，白天很小.在冰温垂直分布中20cm冰层温度有时可出现极大值.冰面热量收支计算表明，夜间冰面辐射冷却损失热量主要由冰层向冰面热量输送来补偿.白天冰层的热量主要来源于穿透短波辐射，冰面和以下冰层间的热量交换很低.白天冰面冰雪融化热量是不可忽视的. 相似文献
3.
水库冰气泡含量和密度对探地雷达测厚的影响分析(英文) 总被引：2，自引：0，他引：2
在水库现场试验了RIS K2型探地雷达探测水库冰厚度的能力,试验时所用天线频率为600MHz;同步钻孔测量雷达探测处的冰厚度;以及在一个点上取样测试分析冰晶体、冰内气泡和冰密度。试验时冰面积雪厚度0.03-0.05m,冰层上部有0.24m粒状冰,其下均为柱状冰;冰内气泡含量呈表层高底层低分布;冰密度随气泡含量变化;冰厚度在平面内不均一。通过探测厚度和实测厚度的对比分析以及气泡含量对介电系数影响的理论分析,建立了积雪、粒状冰和柱状冰三层介质模型,获取雷达波在冰内的理论传递时间。结果发现:能够利用等效介电常数或等效传播速度评价雷达波传递时间,结冰期冰层1/3深度处的对应介电常数或传递速度可以作为等效值;另外因冰内大气泡造成的理论传递时间大于雷达探测时间,其差值随理论传递时间或冰厚的增加呈非线性增加。 相似文献
4.
乌梁素海湖冰晴天反照率日变化具有双峰特征，利用当地太阳高度角同经纬度和儒历的关系，归一化到北京时，依此表达湖冰反照率日变化规律.基于具有指数函数形式的拉普拉斯、高斯、耿贝尔和柯西4种概率密度分布函数建立线性组合模型，对日出后到日落前太阳高度角大于5°时段内的反照率日变化数据进行拟合，发现拉普拉斯密度分布函数组合是最佳统计模型.它既能拟合太阳高度角大于5°时间范围内反照率日变化曲线的双峰特征，又能反映太阳高度角大于15°时间范围内反照率日变化曲线双峰之间的U型分布.该模型不仅形式简单，而且意义明确：尺度参数约为日长的一半，双峰位置与日出时刻关系密切；同时能体现2个反照率峰值的不对称性.为发展不同地区湖冰反照率日变化参数化方案奠定基础. 相似文献
5.
2010年春季至夏季在中山站附近的固定冰面开展了固定冰反照率观测.在春夏过渡期,观测期间的表面反照率呈下降趋势,平均反照率从9月的0.80下降到12月的0.62,整个观测期间的平均值为0.70.雪厚是影响反照率变化的重要因子,融化前期的反照率受表面温度影响较大,干雪期反照率对表面温度并不敏感.降雪可通过增加表面雪厚和减小表面积雪粒径显著增加反照率,云层则可通过吸收入射太阳光中的近红外波段增加反照率,降雪和阴天反照率可比晴天观测平均增加0.18和0.06;吹雪则可通过改变积雪光学厚度导致反照率发生显著变化.受太阳天顶角变化和积雪变性的共同影响,晴天或少云时的反照率在上午随太阳天顶角呈准线性递减,下午则几乎不发生变化;最高值、最低值分别出现在凌晨和下午.本文提出了一组分别表述厚干雪、薄干雪和湿雪反照率日变化的参数化方案,通过太阳天顶角的线性函数隐式考虑进了积雪变性的影响.相比常数反照率方案,该参数化方案能有效提高对反照率日变化的估算能力. 相似文献
6.
北冰洋夏季开阔洋面和浮冰近地层热量平衡参数的观测估算 总被引：18，自引：3，他引：18
利用中国北极科学考察队在北冰洋浮冰站和“雪龙号”考察船获得的大气边界层观测资料, 采用涡旋相关法和廓线法对1999年8月19~24日北冰洋浮冰和开阔水面近地层的热量平衡参数进行了估算. 结果表明, 冰面的净辐射仅为开阔海面的8%, 主要消耗于感热输送和融化, 冰面损失的热量超过了吸收的净辐射, 并由冰的深层热传导来补偿, 潜热通量对冰面热平衡的贡献较小. 开阔海面吸收的净辐射主要以潜热和感热向大气输送, 分别占52%和25%, 剩余部分向深层水体传导. 观测事实说明北冰洋夏季开阔海面/大气和冰面/大气之间的热量交换过程有显著差异, 开阔洋面有大量的水汽向大气输送, 这对研究北冰洋地区海/冰/气相互作用对气候过程的影响是十分重要的. 相似文献
7.
《应用地球物理》2016,(1)
中国第21次(2004/2005,CHINARE 21)和第29次(2012/2013,CHINARE 29)南极科学考察在东南极冰盖伊丽莎白公主地中国泰山考察站站址所在区域,通过探地冰雷达和GPS进行了两次地球物理探测。使用中心频率分别为60MHz和150MHz的冰雷达探测,首次(2004/2005)获得该地区的冰厚与冰内部等时层结构。GPS观测显示以泰山站站址为中心约2km×2km范围内的冰盖表面地形起伏很小,海拔为2607-2636m。冰盖雷达断面显示该区域的平均冰厚为1900m,最大冰厚为1949m,最小冰厚为1856m。在泰山站站址下方冰厚为1870m。冰盖表面高程与冰厚数据联合分析发现该地区的冰下地形相对起伏剧烈,海拔为662-770m,反映出冰下地形为山地地貌。该2km×2km测量网格下方的冰量为7.6km3。60MHz冰雷达数据给出一条长17.6km,穿越泰山站的冰盖断面内部等时层结构图。从中识别分析出一些内部等时层,结果表明该处的冰盖内部等时层受到了冰流的扰动,内部等时层的几何形态暗示了泰山站所处的冰盖下方很可能经历了一个复杂的沉积过程。 相似文献
8.
流动性是冰川的一个主要特征,监测其流速变化可以为冰川物质平衡和冰川灾害研究提供重要信息.本文研究利用2007-2008年的7景ALOS/PALSAR影像和偏移量跟踪技术提取亚洲最大的山岳冰川之一--南伊内里切克冰川的运动场.ALOS/PALSAR影像的时间连续性和南伊内里切克冰川的冰碛覆盖为SAR偏移量跟踪技术获取连续的冰川表面流速提供了基础,然而冰川积累区降雪、附加冰带消融、陡坡区域裂缝发育等客观事件的发生对速度的获取仍有局部影响.尽管如此,本文仍得到了整个冰川不同季节的平面运动场,并且在所有6个时间段内观测到的运动场非常吻合.详细地分析揭示南伊内里切克冰川运动具备以下规律:流速由轴部向两侧递减,由源头向下至雪线处运动速度逐渐增加,然后再向末端逐渐递减;流速大小和坡度大小呈非线性正相关,坡度从1°突变至16°时,冰川运动加速会导致裂缝发育;夏季受冰川湖影响,尾部分支流速能激增至96 cm/d;暖季速度会高于寒季5～10 cm/d.该冰川的冰舌主体日平均速度为20～50 cm/d,局部最高速度可以达到65 cm/d.在冰舌上提取了一些样点的速度作统计,结果显示各个时段中所有样点的平均速度最高可达33.3 cm/d,最低可至27.9 cm/d.冰舌部分的速度和2004年的数据相比下降了约5 cm/d. 相似文献
9.
洱海湖气界面水汽和二氧化碳通量交换特征 总被引：2，自引：0，他引：2
基于2012年涡动相关法取得的洱海湖气之间湍流通量资料,计算了湖面反照率、空气动力学粗糙度和整体输送系数等湖气交换过程的基本物理参数;分析高原湖泊表面动量通量、感热通量、潜热通量和二氧化碳通量的变化特征及其主要的控制因子;采用神经网络法对缺失蒸发量数据进行填补,估算了洱海湖面全年蒸发量。2012年全年蒸发量为（1165±15）mm,大于年实际降水量（2012年的年降水量为818mm）。洱海局地环流在全年范围内较显著;全年主导风向为东南（谷风／湖风）和西北风（山风／陆风）。高原湖泊感热通量通常只有每平方米几十瓦,通常午后感热通量为负值;即湖面向大气输送热量。夏季湖泊大气界面感热通量最大值出现在清晨,与湖气温差的出现时间一致;在白天湖面的有效能量主要分配为潜热通量;湖气温差和水汽压差分别是感热通量和潜热通量日变化的主要控制因子。湖气界面二氧化碳通量除夏季存在弱的吸收外,其余季节（冬季）表现为弱的排放。湖面反照率的季节变化规律与太阳高度角的季节变动有关,同时湖面反照率与水的浑浊度等有关。与实际观测得到的湖面反照率相比,CLM4湖泊模式在冬季低估（夏季高估）了湖面反照率。 相似文献
10.
《应用地球物理》2016,(1)
冰厚和冰下地形是南极冰盖的基本特征参数,是南极冰盖底部环境和物质平衡研究的基础。2007/08年,中国第24次南极科学考察期间,运用深部探测冰雷达系统,在东南极位于Dome A区域的我国南极昆仑站周边,开展了沿"中国墙"的冰厚和冰下地形探测。结果显示:沿"中国墙"的冰厚主要分布在1600m-2800m之间,冰厚最大达到3444m,最小为1255m;冰下地形平均高程为1722m,但是最低仅有604 m;相较于分冰岭北侧,分冰岭南侧冰厚较大,冰下地形较低,并且发育了4个明显的冰下深谷。不过,没有发现Gamburtsev冰下山脉区域典型的冰底再冻结现象以及冰下湖和水体的存在。Bedmap 2中沿"中国墙"的冰厚和冰下地形数据与冰雷达测量结果存在一致性,但是分辨率和在冰下地形起伏剧烈区域的准确性上非常有限。通过冰雷达探测得到的沿"中国墙"的冰厚和冰下地形分布,进一步揭示了这一"不可接近区域"的冰盖特征,对于Dome A区域冰盖动力学研究和未来针对Gamburtsev冰下山脉的地质钻探以及深冰芯钻探选址具有重要参考价值。 相似文献
11.
Sensitivity of physical lake processes to climate change within a large Precambrian Shield catchment 
下载免费PDF全文
下载免费PDF全文 Potential future changes in lake physical processes (e.g. stratification and freezing) can be assessed through exploring their sensitivity to climate change, and assessing the current vulnerability of different lake types to plausible changes in meteorological drivers. This study quantifies the impacts of climate change and sensitivity of lake physical processes within a large (5100 km2) Precambrian Shield catchment in south‐central Ontario. Historic regional relationships are established between climate drivers, lake morphology, and lake physical changes through generalized linear modelling (GLM), and are used to quantify likely changes in timing of ice phenology and lake stratification across 72 lakes under a range of future climate models and scenarios. In response to projections of increased temperature (ensemble mean of +3.3 °C), both earlier ice‐off and onset of summer stratification were projected, with later ice‐on and fall turnover compared to the baseline. Process sensitivity to climate change varied by lake type; shallower lakes with a smaller volume (less than 15 m deep and less than 0.05 km3) were more sensitive to processes associated with lake heating (stratification onset and ice‐off), and deeper lakes with a larger surface area (greater than 30 m deep and greater than 1000 ha) were more sensitive to processes associated with lake cooling (fall turnover and ice‐on). These results indicate that whereas small lakes are vulnerable to climate warming because of changes that occur in spring and summer, larger lakes are particularly sensitive during the fall. The findings suggest that lake morphology and associated sensitivity should be considered in the development of sustainable lake management strategies. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
12.
与非冰封期水体相比，冰封期湖泊初级生产力的研究较为薄弱，一方面在于完整冰封期的调查观测数据仍然较少，而完整的冰下初级生产力变化过程对于理解冰下生态系统对环境因子的响应至关重要，另一方面物理过程与冰下生态的联系仍然有待明确。本研究于2021 2022年冬季期间在大辽河口沿岸的含章湖开展野外调查，通过垂向归纳模型（vertically generalized production model,VGPM）计算了冰下初级生产力，分析了冰封期中初级生产力完整的变化过程，并探讨了冰封期初级生产力的关键物理驱动因素。结果表明：冰封期初级生产力呈现波动爬升的趋势，平均值为0.20 g C/（m2·d）；整个冰封期可以划分为3个时期，即结冰期、缓慢融冰期和快速融冰期，不同时期初级生产力的关键驱动因子不同，在结冰期水温是控制初级生产力的关键因素，在缓慢融冰期冰水界面光合有效辐射强度（photosynthetically active radiation,PAR）是控制初级生产力的关键因素，在快速融冰期水温和冰水界面PAR同时控制初级生产力。在结冰期冰下水体富营养化程度逐渐增加，在融冰期初级生产力随着升温和... 相似文献
13.
Lake ice supports a range of socio‐economic and cultural activities including transportation and winter recreational actives. The influence of weather patterns on ice‐cover dynamics of temperate lakes requires further understanding for determining how changes in ice composition will impact ice safety and the range of ecosystem services provided by seasonal ice cover. An investigation of lake ice formation and decay for three lakes in Central Ontario, Canada, took place over the course of two winters, 2015–2016 and 2016–2017, through the use of outdoor digital cameras, a Shallow Water Ice Profiler (upward‐looking sonar), and weekly field measurements. Temperature fluctuations across 0°C promoted substantial early season white ice growth, with lesser amounts of black ice forming later in the season. Ice thickening processes observed were mainly through meltwater, or midwinter rain, refreezing on the ice surface. Snow redistribution was limited, with frequent melt events limiting the duration of fresh snow on the ice, leading to a fairly uniform distribution of white ice across the lakes in 2015–2016 (standard deviations week to week ranging from 3 to 5 cm), but with slightly more variability in 2016–2017 when more snow accumulated over the season (5 to 11 cm). White ice dominated the end‐of‐season ice composition for both seasons representing more than 70% of the total ice thickness, which is a stark contrast to Arctic lake ice that is composed mainly of black ice. This research has provided the first detailed lake ice processes and conditions from medium‐sized north‐temperate lakes and provided important information on temperate region lake ice characteristics that will enhance the understanding of the response of temperate lake ice to climate and provide insight on potential changes to more northern ice regimes under continued climate warming. 相似文献
14.
Glaciers and snow cover are important constituents of the surface of the Tibetan Plateau. The responses of these phenomena to global environmental changes are sensitive, rapid and intensive due to the high altitudes and arid cold climate of the Tibetan Plateau. Based on multisource remote sensing data, including Landsat images, MOD10A2 snow product, ICESat, Cryosat-2 altimetry data and long-term ground climate observations, we analysed the dynamic changes of glaciers, snow melting and lake in the Paiku Co basin using extraction methods for glaciers and lake, the degree-day model and the ice and lake volume method. The interaction among the climate, ice-snow and the hydrological elements in Paiku Co is revealed. From 2000 to 2018, the basin tended to be drier, and rainfall decreased at a rate of −3.07 mm/a. The seasonal temperature difference in the basin increased, the maximum temperature increased at a rate of 0.02°C/a and the minimum temperature decreased at a rate of −0.06°C/a, which accelerated the melting from glaciers and snow at rates of 0.55 × 107 m3/a and 0.29 × 107 m3/a, respectively. The rate of contribution to the lake from rainfall, snow and glacier melted water was 55.6, 27.7 and 16.7%, respectively. In the past 18 years, the warmer and drier climate has caused the lake to shrink. The water level of the lake continued to decline at a rate of −0.02 m/a, and the lake water volume decreased by 4.85 × 108 m3 at a rate of −0.27 × 108 m3/a from 2000 to 2018. This evaluation is important for understanding how the snow and ice melting in the central Himalayas affect the regional water cycle. 相似文献
15.
Thermokarst lakes play a key role in the hydrological and biogeochemical cycles of permafrost regions. Current knowledge regarding the changes caused by permafrost degradation to the hydrochemistry of lakes in the Qinghai-Tibet Plateau (QTP) is limited. To address this gap, a systematic investigation of thermokarst lake water, suprapermafrost water, ground ice, and precipitation was conducted in the hinterland of the QTP. The thermokarst lake water in the QTP was identified to be of the Na-HCO3-Cl type. The mean concentrations of HCO3− and Na+ were 281.8 mg L−1 (146.0–546.2 mg L−1) and 73.3 mg L−1 (9.2–345.8 mg L−1), respectively. The concentrations of Li+, NH4+, K+, F−, NO2−, and NO3− were relatively low. Freeze-out fractionation concentrated the dissolved solids within the lake water during winter, which was deeply deepened on lake depth and lake ice thickness. Owing to solute enrichment, the ground ice was characterized by high salinity. Conversely, repeated replenishment via precipitation led to lower solute concentrations in the ground ice near the permafrost table compared to that within the permafrost. Although lower solute concentration existed in precipitation, the soil leaching and saline ground ice melting processes enhanced the solute load in suprapermafrost water, which is considered an important water and solute resource in thermokarst lakes. The influencing mechanism of permafrost degradation on thermokarst lake hydrochemistry is presumably linked to: (1) the liberation of soluble materials sequestered in ground ice; (2) the increase of solutes in suprapermafrost water and soil pore water; and (3) the changes in lake morphometry. These results have major implications on the understanding of the effects of ground ice melting on ecosystem functions, biogeochemical processes, and energy balance in a rapidly changing climate. 相似文献
16.
The formation of ice cover on lakes alters heat and energy transfer with the water column. The fraction of surface area covered by ice and the timing of ice-on and ice-off therefore affects hydrodynamics and the seasonal development of stratification and related ecosystem processes. Multi-year model simulations of temperate lake ecosystems that freeze partially or completely therefore require simulation of the formation and duration of ice cover. Here we present a multi-year hydrodynamic simulation of an alpine lake with complex morphology (Lower Lake Constance, LLC) using the three-dimensional (3D) model Aquatic Ecosystem Model (AEM3D) over a period of 9 years. LLC is subdivided into three basins (Gnadensee, Zeller See and Rheinsee) which differ in depth, morphological features, hydrodynamic conditions and ice cover phenology and thickness. Model results were validated with field observations and additional information on ice cover derived from a citizen science approach using information from social media. The model reproduced the occurrence of thin ice as well as its inter-annual variability and differentiated the frequency and extent of ice cover between the three sub-basins. It captured that full ice cover occurs almost each winter in Gnadensee, but only rarely in Zeller See and Rheinsee. The results indicate that the 3D model AEM3D is suitable for simulating long-term dynamics of thin ice cover in lakes with complex morphology and inter-annual changes in spatially heterogeneous ice cover. 相似文献
17.
Claude R. Duguay Greg M. Flato Martin O. Jeffries Patrick Mnard Kim Morris Wayne R. Rouse 《水文研究》2003,17(17):3465-3483
A one‐dimensional thermodynamic model for simulating lake‐ice phenology is presented and evaluated. The model can be driven with observed daily or hourly atmospheric forcing of air temperature, relative humidity, wind speed, cloud amount and snowfall. In addition to computing the energy balance components, key model output includes the temperature profile at an arbitrary number of levels within the ice/snow (or the water temperature if there is no ice) and ice thickness (clear ice and snow‐ice) on a daily basis, as well as freeze‐up and break‐up dates. The lake‐ice model is used to simulate ice‐growth processes on shallow lakes in arctic, sub‐arctic, and high‐boreal forest environments. Model output is compared with field and remote sensing observations gathered over several ice seasons. Simulated ice thickness, including snow‐ice formation, compares favourably with field measurements. Ice‐on and ice‐off dates are also well simulated when compared with field and satellite observations, with a mean absolute difference of 2 days. Model simulations and observations illustrate the key role that snow cover plays on the seasonal evolution of ice thickness and the timing of spring break‐up. It is also shown that lake morphometry, depth in particular, is a determinant of ice‐off dates for shallow lakes at high latitudes. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
18.
Hazardous processes and events from glacier and permafrost areas: lessons from the Chilean and Argentinean Andes 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 Glacier and permafrost hazards such as glacial‐lake outburst floods and rock–ice avalanches cause significant socio‐economic damages worldwide, and these processes may increase in frequency and magnitude if the atmospheric temperature rises. In the extratropical Andes nearly 200 human deaths were linked to these processes during the twentieth century. We analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio‐economic damages in this region in historic time (including glacial lake outburst floods, ice and rock–ice avalanches and lahars) to unravel their causes and geomorphological impacts. In the extratropical Andes, at least 15 ice‐dammed lakes and 16 moraine‐dammed lakes have failed since the eighteenth century, causing dozens of floods. Some floods rank amongst the largest events ever recorded (5000 × 106 m3 and 229 × 106 m3, respectively). Outburst flood frequency has increased in the last three decades, partially as a consequence of long‐term (decades to centuries) climatic changes, glaciers shrinkage, and lake growth. Short‐term (days to weeks) meteorological conditions (i.e. intense and/or prolonged rainfall and high temperature that increased meltwater production) have also triggered outburst floods and mass movements. Enormous mass failures of glaciers and permafrost (> 10 × 106 m3) have impacted lakes, glaciers, and snow‐covered valleys, initiating chain reactions that have ultimately resulted in lake tsunamis and far‐reaching (> 50 km) flows. The eruption of ice‐covered volcanoes has also caused dozens of damaging lahars with volumes up to 45 × 106 m3. Despite the importance of these events, basic information about their occurrence (e.g. date, causes, and geomorphological impact), which is well established in other mountain ranges, is absent in the extratropical Andes. A better knowledge of the processes involved can help to forecast and mitigate these events. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献